The present invention is related to pipe assemblies, e.g., vent or flue systems for gas-fired appliances such as furnaces.
One system which is currently used for flues or vents for gas-fired appliances (such as furnaces) utilizes a series of unthreaded essentially cylindrical pipes and fittings (tees, elbows, etc.) made from high temperature resistant resins. When these systems are assembled, it is essential that there be a leak-proof seal at each joint so that the products travelling through the vent or flue (such as Hcl, H.sub.2 SO.sub.4 and HNO.sub.3) do not escape from the vent or flue until they reach the end of the vent or flue. Since the flue or vent is assembled by merely inserting a male end of, e.g., a pipe into a female end of, e.g., a fitting (i.e., there are no threads or other mechanical means to hold the joint together), providing a leak-free seal at each joint can be a problem.
The problem of providing a leak-proof seal has been addressed by applying a bead of sealant to the outer surface of the female portion of the joint assembly prior to inserting it into the male portion of the assembly. After the sealant cures, it seals the joint and provides the desired leak-proof properties.
One serious problem with sealing the vent or flue system using only a sealant is that the sealant does not cure rapidly, and, in fact, can be rather slippery until it cures. As the various pieces of the flue or vent are assembled, joints which have already been assembled can slip or move because the sealant has not yet cured. This can result in a loss of integrity of the seals in the joints already assembled.
One answer to the problem of joint slippage is to immobilize the joint until the sealant cures enough to form a tight seal. This can, of course, be done by manually holding each joint together until the sealant cures. However, since the curing time for typical sealants is several hours, this solution to the slippage problem is impractical at best.
Thus, there has existed a need for a way to conveniently hold the joints of the flue or vent system immobile as the flue or vent is being assembled so that the sealant can cure without adversely affecting the seal.
One proposed method for holding the flue or vent joints while the flue or vent is being assembled is to fasten a barbed metal clip over the end of the male portion of the joint so that, when the joint is assembled, the barbs grip the outer surface of the male portion and the inner surface of the female portion of the joint. While these metal clips do provide some added stability to the joint, they suffer from several serious drawbacks.
First, the barbed clips are hard and sharp and often scratch the pipes' surfaces as well as putting the pipe under stress at the points of contact between the pipes and clips. This can lead to fracturing of the pipe, a clearly undesirable result in a system which is supposed to be leak-free.
Secondly, the metal clips are subject to corrosion by the products carried by the flue or vent, such as Hcl, H.sub.2 SO.sub.4 and/or HNO.sub.3. This corrosion can lead to long term failure of the clip and joint.
Another disadvantage of the barbed metal clips is that generally they are thicker than the space between the outer surface of the male portion and the inner surface of the female portion of the joint. Thus, as the metal clip is forced between the male and female portions of the joint, the pipes are deformed and a gap forms between the pipes where each clip is attached. This is obviously undesirable if a leak-proof joint is to be achieved.
It has now been found that if an elastomeric tape having the configuration described herein is applied to the male portion of the joint prior to assembly, the resulting joint is stabilized against movement without otherwise adversely affecting the joint seal. Thus, the sealant is allowed to cure without having the joint shift or slip.
Among other factors, the present invention is based upon the discovery that when an elastomeric tape, as described herein, is used in a pipe joint assembly, the resulting assembly is stabilized against movement. Furthermore, it has been discovered that the strength of the resulting joint is improved significantly over previous joint assemblies. Also, the elastomeric tape provides a sealing means in the joint assembly.